1. Field of the Invention
The invention is directed to an improved device and a method for producing a medium for the treatment of exhaust gases from an internal combustion engine.
2. Description of the Prior Art
In Otto and diesel engines, exhaust gas cleaning is gaining ever-increasing significance. In the superstoichiometric exhaust gas, that is, in lean operation of an Otto engine or in the operation of a diesel engine, the nitrogen oxides that occur in combustion cannot be adequately decomposed, because of the oxygen excess. Therefore, even in diesel vehicles, extensive exhaust gas posttreatment with regard to particle emissions and NOx. emissions is necessary. To reduce NOx emissions, the NOx storage-type catalytic converters are attractive. They store nitrogen oxides even under superstoichiometric conditions. As the quantity of stored nitrogen oxides increases, the storage capacity decreases, so that the storage-type catalytic converter must be cleaned out again or regenerated at regular intervals. This is possible only in a reducing environment; that is, rich exhaust gas conditions (lambda value <1) must first be established. From German Patent Disclosure DE 100 62 956, it is also known to generate a reducing agent on board the motor vehicle, outside the exhaust gas line of the internal combustion engine of a motor vehicle, and to supply it downstream of the engine to the exhaust gas before entry into a deNOx catalytic converter.